James R Frankenberger

Geospatial Application of the Water Erosion Prediction Project (WEPP) Model

Abstract. At the hillslope profile and/or field scale, a simple Windows graphical user interface (GUI) is available to easily specify the slope, soil, and management inputs for application of the USDA Water Erosion Prediction Project (WEPP) model. Likewise, basic small watershed configurations of a few hillslopes and channels can be created and simulated with this GUI. However, as the catchment size increases, the complexity of developing and organizing all WEPP model inputs greatly increases due to the multitude of potential variations in topography, soils, and land management practices. For these types of situations, numerical approaches and special user interfaces have been developed to allow for easier WEPP model setup, utilizing either publicly available or user-specific geospatial information, e.g., digital elevation models (DEMs), geographic information system (GIS) soil data layers, and GIS land use/land cover data layers. We utilize the Topographic Parameterization (TOPAZ) digital landscape analysis tool for channel, watershed, and subcatchment delineation and to derive slope inputs for each of the subcatchment hillslope profiles and channels. A user has the option of specifying a single soil and land management for each subcatchment or utilizing the information in soils and land use/land cover GIS data layers to automatically assign those values for each grid cell. Once WEPP model runs are completed, the output data are analyzed, results interpreted, and maps of spatial soil loss and sediment yields are generated and visualized in a GIS. These procedures have been used within a number of GIS platforms including GeoWEPP, an ArcView/ArcGIS extension that was the first geospatial interface to be developed in 2001. GeoWEPP allows experienced GIS users the ability to import and utilize their own detailed DEM, soil, and/or land use/land cover information or to access publicly available spatial datasets. A web-based GIS system that used MapServer web GIS software for handling and displaying the spatial data and model results was initially released in 2004. Most recently, Google Maps and OpenLayers technologies have been integrated into the web WEPP GIS software to provide significant enhancements. This article discusses in detail the logic and procedures for developing the WEPP model inputs, the various WEPP GIS interfaces, and provides example real-world geospatial WEPP applications. Further work is ongoing in order to expand these tools to allow users to customize their own inputs via the internet and to link the desktop GeoWEPP with the web-based GIS system.

GeoWEPP - The Geo-spatial interface for the Water Erosion Prediction Project

Decision-makers operating at different scales of interest and responsibility have to assess the distribution, extent, and severity of soil erosion and sedimentation. To seek solutions in handling natural and human actions related to this type of nonpoint source pollution, the linkage of distributed assessment models and Geographical Information Systems (GIS) at various spatial and temporal scales is in high demand. The Water Erosion Prediction Project (WEPP) model is a continuous simulation, process-based model that allows simulation of water and sediment balance in small watersheds and on hillslope profiles within those watersheds. This presentation introduces an approach for running WEPP simulations based on using available geo-spatial information through a linkage with GIS. The new Geo-spatial interface for WEPP (GeoWEPP) utilizes readily available digital geo-referenced information from publicly accessible Internet sources such as the U.S. Geological Survey digital elevation models, topographical maps, and land use data as well as Natural Resources Conservation Service soils maps. Together with parameter sets of the WEPP database containing statistical parameter sets from more than 2600 U.S. climate stations, GeoWEPP enables even non-GIS-and-modeling users to derive and prepare valid model input parameters to assess representative conditions in an area of interest. After establishing the main data input for a particular site, various land use scenarios can be evaluated to assist with soil and water conservation planning.

Impact of precipitation changes on runoff and soil erosion in Korea using CLIGEN and WEPP

The quality of spatially and temporally distributed weather information is critical in soil erosion model results because of the primary influence of rainfall on runoff and soil movement. Detailed climate data for the Water Erosion Prediction Project (WEPP) model can be generated by a climate generator (CLIGEN) based on long-term statistical parameters for more than 4,000 locations in the United States. The objectives of this study were to apply CLIGEN and WEPP and examine the effects of changing storm frequency, storm depth, or a combination of the two on predicted rainfall, runoff, and soil loss. Two different sites, Chun-Cheon and Jeon-Ju, were studied and compared for the period 1966 to 2005. Chun-Cheon is located at a higher altitude and is surrounded with forest, while Jeon-Ju is located in the plains. CLIGEN was used to generate 100-year climate sequences with daily climate data e.g., temperature, precipitation, wind, and solar radiation for a representative climate station in the study sites to predict runoff and soil loss with WEPP. Three precipitation change scenarios were examined in this study: (1) adjusting the number of days with rainfall, (2) adjusting the mean amount of rainfall on a wet day, and (3) a combination of 1 and 2. Observed mean annual precipitation at Chun-Cheon (1,305 mm [50.9 in]) was similar to Jeon-Ju (1,291 mm [50.4 in]). CLIGEN simulated mean annual precipitation depths in Chun-Cheon and Jeon-Ju were very close to the observed data. The WEPP model predicted runoff in Jeon-Ju was 48.8% higher than that in Chun-Cheon and estimated soil loss in Chun-Cheon was 55.6% higher than that in Jeon-Ju. Precipitation change scenario 3 that combined changes in precipitation occurrence with changes in rainfall storm depths showed the largest impacts on predicted runoff and soil loss. A combined 20% increase in these precipitation parameters resulted in increases of 44%, 54%, and 52% in generated average annual precipitation, predicted runoff and predicted soil loss, respectively, at Chun-Cheon, while increases at Jeon-Ju were 44%, 60%, and 27%. Increases in rainfall due to future climate change may thus potentially result in substantial and nonlinear increases in runoff and soil loss in Korea.

Development of a GIS Interface for WEPP Model Application to Great Lakes Forested Watersheds

This presentation will highlight efforts on development of a new online WEPP GIS interface, targeted toward application in forested regions bordering the Great Lakes. The key components and algorithms of the online GIS system will be outlined. The general procedures used to provide input to the WEPP model and to display model output will be demonstrated.

Web-based GIS Application of the WEPP Model

WEPP (Water Erosion Prediction Project) is a process-based, distributed parameter, continuous simulation erosion prediction model. Work over the past several years has focused on development of improved user interfaces and linkage of WEPP to Geographic Information Systems (GIS) that can allow rapid and impartial delineation of watersheds and topographic features based upon digital elevation data. However, many potential users of WEPP have little or no experience with commercial GIS packages, and that software can also be quite expensive. This paper discusses a web-based WEPP-GIS system that only requires a user to have a network connection and web browser. GIS Viewer software allows users to specify an area of interest to model with WEPP, then digital elevation data for the area is sent to topographic parameterization software to delineate watersheds, channels and hillslopes. The digital elevation data are processed on the server side, and then images of the delineated watershed and hillslopes are passed to the user’s web-browser window. Once the hillslopes and channels have been located, WEPP model simulations of representative hillslope profiles and channels, and/or all flowpaths in the watershed, are conducted. The modeled soil erosion results in graphical format are sent as images to the client computer. Subsequent model simulations using different land management practices can help to show the impact of conservation practices on runoff and soil erosion.

IMPROVING FROST-SIMULATION SUBROUTINES OF THE WATER EROSION PREDICTION PROJECT (WEPP) MODEL

Erosion models play an important role in assessing the influence of human activities on the environment. For cold areas, adequate frost simulation is crucial for predicting surface runoff and water erosion. The Water Erosion Prediction Project (WEPP) model is a physically based erosion prediction software program developed by the USDA. One of the major components of WEPP is the simulation of winter processes, which include snow accumulation and melt as well as soil freeze and thaw. WEPP is successfully used in the evaluation of important natural resource issues throughout the U.S. and in a number of other countries. However, previous studies revealed problems in the winter component of the WEPP model, especially the routine for frost simulation. The main purpose of this study was to improve the WEPP model (v2006.5) by changing the soil profile discretization and computation of key thermal and hydraulic parameters in the frost simulation routines so that the model can adequately simulate soil freeze-thaw and winter runoff and erosion. WEPP v2006.5 and the modified version (v2010.1) were applied to experimental plots in Pullman, Washington, and Morris, Minnesota. The simulated snow and frost depths as well as runoff and sediment yield were contrasted and compared with field observations; the results from v2010.1 showed substantial improvement compared to those from v2006.5.

Geospatial application of the Water Erosion Prediction Project (WEPP) model

The Water Erosion Prediction Project (WEPP) model is a process-based technology for prediction of soil erosion by water at hillslope profile, field, and small watershed scales. In particular, WEPP utilizes observed or generated daily climate inputs to drive the surface hydrology processes (infiltration, runoff, ET) component, which subsequently impacts the rest of the model, including subsurface hydrology (percolation, subsurface lateral flow), hillslope erosion (interrill & rill detachment, sediment transport & deposition), channel hydrology/erosion (channel flow routing, detachment, sediment transport, deposition), plant growth, and residue decomposition. At the hillslope profile and/or field scale, simple Windows graphical user interfaces (GUIs) have been developed to easily specify the slope, soil, and management inputs. Likewise, simple watershed configurations of a few hillslopes and channels can be easily created and simulated with this GUI. However, as the catchment size increases, the complexity of developing and organizing all WEPP model inputs greatly increases, due to the multitude of potential variations in topography, soils, and land management practices. For these types of situations, numerical approaches and special user interfaces have been developed to allow for easier WEPP setup, utilizing either publicly-available or user-specific geospatial information (Digital Elevation Models (DEMs), Geographic Information System (GIS) soil layers, GIS land-use layers). The basic approach used to automatically generate the slope input files for hillslope profiles is to analyze and process a DEM of an area in three iterations: 1) channel network delineation, 2) watershed boundary and subcatchment delineation, and 3) flow-path and representative hillslope profile determination. The TOPAZ digital landscape analysis tool is used for channel, watershed, and subcatchment delineation. In whichever interface is being used, once a user selects a rectangular region of interest within a DEM, TOPAZ delineates the network of channels within that region. The user then selects the outlet point on a channel for their watershed of interest, after which TOPAZ is run again to delineate the watershed boundary and its subcatchments (that will subsequently be used as WEPP hillslopes). The final step before the actual erosion model simulations is to create the slope, soil and management input files for WEPP, using custom software (called Prepwepp) taking data from the extracted land use, soils, DEM, and TOPAZ watershed structures. Specifically, in regards to the hillslope profile slope inputs, there are two options for running WEPP: 1) creating a single representative hillslope profile slope input for each subcatchment based upon an averaging of all the computed flowpaths within a subcatchment; and/or 2) running WEPP model simulations for all TOPAZ-identified flowpaths within each subcatchment. The model slope inputs for each of the channels within the delineated watershed also are obtained from the TOPAZ output. A user has the option of specifying a single soil and land management for each subcatchment, or utilizing information in soil and land use GIS layers to automatically assign these. Once WEPP runs are completed, output is scanned (by Prepwepp), results interpreted, and maps of spatial soil loss are generated and sent to the GIS for display. These procedures have been used within a number of GIS platforms. GeoWEPP is an ArcView/ ArcGIS extension that was the first to be developed, and which allows experienced GIS users the ability to import and utilize their own detailed DEM, soil, and/or land use information, or to access commonly available spatial datasets. An initial web-based GIS system that uses the MapServer web GIS software for handling and displaying the spatial data and model results was released in 2004. Most recently, the Google Maps and OpenLayers technologies have been integrated into the web GIS software and WEPP model to provide some significant enhancements over the earlier prototype. This presentation will discuss in detail the logic and procedures for developing the WEPP model inputs, a variety of WEPP GIS interfaces, and future directions.

Applying Online WEPP to Assess Forest Watershed Hydrology

Abstract. A new version of the online Water Erosion Prediction Project (WEPP) GIS interface has been developed to assist in evaluating sediment sources associated with forests and forest management within the Great Lakes basin. WEPP watershed structure and topographical inputs for each watershed element are generated from the USGS 30 m National Elevation Dataset (NED), soil inputs are automatically retrieved from the USDA-NRCS SSURGO database, and land use and management inputs are selected from the WEPP database based on the USGS National Land Cover Database 2001 (NLCD2001). Additionally, ground cover and soil properties of the WEPP management and soil input files can be customized to represent site-specific conditions. Daily climate inputs are generated from long-term climate parameters using CLIGEN, a stochastic climate generator embedded in the online interface. Alternatively, a registered user can upload and use observed daily climate data for online WEPP simulation. Long-term observational data, including runoff and water chemistry, from two mature forest watersheds of the Fernow Experimental Forest in West Virginia were used to assess the online WEPP GIS interface. Online WEPP simulations were carried out using both observed and CLIGEN-generated climate inputs, and model performance was examined by comparing simulated and observed runoff and simulated and estimated (from measured water chemistry data) sediment yield. The online WEPP reasonably simulated average annual runoff and the annual maximum runoff series for both watersheds, but overpredicted sediment yield for the annual average and annual maximums. The online WEPP simulation results accurately reflected the differences between the two watersheds in their hydrological characteristics. The online WEPP GIS interface is a user-friendly, web-based computer package that can be used by scientists, researchers, and practitioners as a cost-effective simulation tool for watershed management.

WEPP Model Application in CEAP Watersheds in NE Indiana

The Conservation Effects Assessment Project (CEAP) of the United States Department of Agriculture (USDA) is targeted at determining the impacts of conservation practices on off-site losses of sediment, nutrients, and pesticides. One of the Agricultural Research Service (ARS) benchmark CEAP watersheds is the St. Joseph River Watershed, located in northeastern Indiana, northwestern Ohio, and southern Michigan. The USDA-ARS National Soil Erosion Research Laboratory (NSERL) in West Lafayette, Indiana, has been conducting field and watershed monitoring in sub-basins of the St. Joseph River watershed since 2002. The area is largely agricultural, with major crops of corn and soybeans. Soils are moderately to poorly drained, and the topography is flat to gently rolling, with large numbers of closed surface depressional areas (potholes). While a number of hydrology and pesticide simulations have been conducted for this location with larger scale watershed models, no detailed modeling of sediment loss has been done up to this point. This paper will describe application of the Water Erosion Prediction Project (WEPP) model to small fields (~2 ha) where detailed measurements of climate, soil properties, topography, management, and storm runoff and sediment loss are available. Adequacy of WEPP model predictions will be evaluated, and model calibration and validation results presented. WEPP was also applied to the next larger scale of watersheds (~250 ha) to determine potential effects of land management practices there on runoff and sediment loss. Some typical alternative management practices evaluated were conservation tillage, buffer strips, and conversion of critically eroding regions to forest or grass.

Regional Scale Application of USLE and WEPP for Soil Erosion Assessment in Korea

Due to the geographical location of Korea in the Asian monsoon belt, more than half of annual precipitation occurs during the summer season (May to September). This causes significant amounts of soil loss from croplands, which is directly linked to the deterioration of surface water quality. Therefore, accurate and real-time estimation of soil erosion has been a great concern in Korea. The purpose of this study is to implement two soil erosion models, the empirical Universal Soil Loss Equation (USLE) and the physical-based model of the Water Erosion Prediction Project (WEPP). Both USLE and WEPP are spatial-distributed regional-scale models. Model input files containing climate, soil, slope and cropping management are modified to consider Korean conditions. Necessary weather data are obtained from the Meteorological Information Web Service System-Disaster Prevention (MISS-DP) of Meteorological Administration in Korea. The Agricultural Soil Information System (ASIS) and Crop Information Center of Rural Development Administration provide soil, slope, and cropping management information for both models. Two cities with different topographic characteristics, Chun-Cheon (forest) and Jeon-Ju (level-plain) in Korea are used to assess the model performance in this study. The results of this study were that better erosion prediction using the WEPP model since it illustrates a higher degree of spatial variability than USLE in topography, precipitation, soils, and crop management practices. There was a little variability between the estimates in Chun-Cheon(r2=0.6841) and Jeon-Ju(r2=0.8891). In addition, the findings of this study were aided in developing the environmental assessment program to conserve the agricultural environment in Korea.